Twitter CEO Dick Costolo is shown Nov. 7, 2013 as Twitter stock was launched in New York. The stock soared to $74 last December, but now is at its lowest point since its IPO. (Richard Drew/Associated Press)

Twitter stock dropped more than 10 per cent overnight because of investor concern about its ability to grow its user base and keep its existing users engaged.

The short messaging service booked a net loss in the first quarter because of stock compensation costs, but its results surpassed Wall Street's expectations thanks to a sharp increase in advertising revenue.

Shares were trading down 10.7 per cent or $4.54 at $38.08 on Wednesday morning, the stock's lowest price since since Twitter went public last fall. They ended the day at $38.71.

Twitter went public last November, setting a price of $26 per share for its stock, which then soared amid hungry investor demand. The high-flying stock peaked in December at $74.73 and then declined sharply.

The company reported having 255 million monthly active users during the quarter, up from 241 million in the December quarter and 204 million in the same quarter a year earlier. But the growth rate of new users was a disappointment to investors, who had expected about 260 million followers by the first quarter.

Revenue doubled on mobile ads

Twitter Inc. said Tuesday that it had a loss of $132.4 million, or 23 cents per share, in the January-March quarter. That compares with a loss of $27 million, or 21 cents per share, a year ago when Twitter was still privately held. Adjusted earnings were $183,000, or roughly breakeven on a per share basis.

Revenue more than doubled to $250 million from $114 million. Twitter's advertising revenue was $226 million, about 80 per cent of which came from mobile advertising.

Analysts polled by FactSet had expected an adjusted loss of three cents per share on revenue of $241.5 million. Twitter's own forecast in February was for revenue between $230 million and $240 million.

The number of new Twitter users is up 25 per cent from a year ago. Sterne Agee analyst ArvindBhatia called the quarter's results "mixed," noting that user metrics were better than they were in the final quarter of 2013 — Twitter's first as a public company — but not as strong as Wall Street had expected.

Twitter encouraging more postings

Twitter has said that it is focusing on expanding its audience and encouraging people who do use its short messaging service to use it more often. By comparison, Facebook has 1.28 billion users and professional networking service LinkedIn had 277 million users at the end of 2013. WhatsApp, the messaging app Facebook has agreed to buy for $19 billion, recently passed the 500 million user milestone.

"We had a very strong first quarter. Revenue growth accelerated on a year over year basis fueled by increased engagement and user growth," said CEO Dick Costolo in a statement.

"Timeline views," which measure how often users refresh their own or someone else's Twitter feed, increased 15 per cent in the quarter to 157 billion. Wall Street had expected of a higher number at 165 billion, according to Bhatia.

Advertising revenue per thousand timeline views, another closely watched measurement, reached $1.44 in the first quarter, more than double the figure from a year ago. But the number declined from the fourth quarter of 2013, when it was $1.49.

Twitter gave a conservative revenue forecast for the current quarter and for all of 2014. The company expects revenue of $270 million to $280 million for the April-June period, compared with analysts' expectations of $273.3 million.

For the full year, Twitter expects revenue of $1.2 billion to $1.25 billion, compared with analysts' forecast of $1.24 billion.